The present invention relates to apparatus for setting the diameter of a tire building drum in which the diameter is set by means of a traveling rod and stop spacers, the varying diameters being to accommodate the construction of tires of different sizes on the same drum.
Among the types of machines used in the assembly of pneumatic tires for motor vehicles is a drum upon which is assembled the tread assembly. The tread assembly generally includes the breaker(s), the overlay and the tread. For the latter arrangement, the machine is called a BOT (belt, overlay, tread) drum. The tread assembly is built separately from the tire carcass because of the inexpansible breaker assembly that lies radially inward of the tread.
Since a given tread building machine, or BOT drum, or machine, can be used to assemble tire treads of different diameters, the cylindrical diameter of the BOT drum is made to be variable, in precisely repeatable ways. The diameter of the machine is adjusted by means of pneumatic pressure acting upon a system of axially moving cams that operate to force the perimeter portions of the machine radially outward.
A given desired diameter of a BOT drum is achieved by applying pneumatic pressure which increases the radius of the machine""s outer perimeter to a limit that is determined by the presence of spacer blocks placed upon two axially aligned and axial movable shafts that are contiguous with the moving cam assembly and located in diametric opposition in relation to the major axis of the drum. If no spacer blocks are used, the axially moving cam will move to its maximum position, thereby opening the drum to its maximum diameter. But when spacer blocks are installed upon the axial shafts, the cam will move only so far as to provide the precise desired BOT diameter. The latter diameter is determined by the size of the spacer blocks used to limit the movement of the cam. In this way, a tire tread assembly of a given diameter can be built. After a given tread assembly is built, the pneumatic pressure can be released so that the diameter of the BOT drum can be reduced (typically by springs) and the tread assembly can be removed from the drum. The pneumatic pressure is then reapplied to the drum in preparation for the next tread building process.
In present BOT drums, two spacer blocks of a given size, and selected from a plurality of sizes, are installed on the two axially aligned shafts to affect a given desired diameter of the BOT drum. This means that for each of the plurality of desired diameters, two spacer blocks of specific size are needed. This also means that a large set of pairs (often about 144 pairs) of spacer blocks are needed and kept in storage for use whenever a different maximum BOT diameter setting is needed.
Such a system of spacer blocks requires that the unused spacer blocks much be stored, accounted for, and be accessible as needed.
A screw type adjustable spacer design is described in U.S. Pat. No. 4,508,498 to Collmann, which is used in relation to a xe2x80x9ctire shaping drum,xe2x80x9d a machine that is used in another phase of the tire building process. The tire shaping drum is used to give the characteristic toroidal shape to a tire carcass, which primarily includes the liner, ply layers and the sidewalls.
A screw type adjustable spacer of the sort taught by Collmann was tried on the BOT drum, but problems were encountered. The most critical was that such a spacer does not have fixed positions which means that once set, it can move and lose its adjustment size from the precise desired spacing distance. Most specifically, the spacer in the Collmann patent has the potential to change with vibration loosening. Also, the length of the Collmann type spacer is infinitely adjustable and the setting is under operator control and the length must be judged by making measurements. Further, the Collmann spacer is too large to fit into the BOT drum application without requiring major modification of the drum.
One aspect of the present invention is to provide a simple replacement for the plurality of spacer blocks employing a single adjustable or universal spacer such that two such spacers can be used on a given BOT drum to achieve the purpose of the plurality of spacer blocks ordinarily used.
Another aspect of the present invention is to make the universal spacer adjustable with regard to its role of replacing the spacer blocks of different sizes.
Yet another aspect of the present invention is to provide a universal spacer that can be easily and rapidly adjusted in fixed and repeatable incremental sizes to accommodate the specific required diameters of a given BOT drum.
According to the present invention, a universal spacer for varying the diameter of a tire tread breaker building drum comprises: a cylindrical outer body portion having a plurality of sets of diametrically opposed holes extending therethrough; an inner cylindrical portion having at least two diametrically opposed holes therethrough for varying the diameter of the tire tread breaker building drum; the inner cylindrical portion is connected by at least one traveling shaft (16) to the building drum for varying the diameter of the building drum; and structural means are provided for interconnecting the outer cylindrical body portion with the inner cylindrical portion to adjust the travel distance of the traveling rod and thereby control the diameter of the building drum.
Also according to the present invention, the structural means for interconnecting the outer cylindrical body portion with the inner body portion is a pin. The pin (36) is slideably engagable through any two diametrically opposed holes in the outer cylindrical body portion and through at least two diametrically opposed holes of the inner cylindrical body portion. One end of the pin is affixed with a finger grasping flange having a ring attached thereto.
Further according to the present invention, the sets of diametrically opposing holes in the outer cylindrical body portion are regularly spaced and are situated so as to comprise a plurality of diametrically opposed hole sets through which the pin can be inserted while also engaging at least two of the diametrically opposing holes in the inner moveable cylindrical body portion in such a way as to provide incremental and repeatable adjustment of the axial relationship of the outer cylindrical body portion and the inner cylindrical body portion.
Also according to the present invention, indicator numbers are located adjacent the holes of the outer cylindrical body portion so as to allow repeatable incremental adjustment of the relative axial positions of the outer cylindrical body portion and the inner cylindrical body portion by the means for interconnecting the outer cylindrical body portion with the inner cylindrical portion.
According to the present invention, the sets of diametrically opposing holes in the outer cylindrical body portion are arranged so as to comprise a regular double helical pattern about the circumference of the outer cylindrical body portion.
According to the present invention, a method of varying the diameter of a tire tread breaker building drum comprises: providing a cylindrical outer body portion having a plurality of sets of diametrically opposed holes extending therethrough; providing an inner cylindrical portion of a having at least two diametrically opposed holes therethrough, the inner cylindrical portion being connected by a traveling shaft to a cam component of the building drum for varying the diameter of the building drum; and interconnecting the outer cylindrical body portion with the inner cylindrical portion to adjust the travel distance of the traveling rod and thereby control the diameter of the building drum.
According to the present invention, the method includes interconnecting the outer cylindrical body portion with the inner body portion is accomplished with a pin.
Also according to the present invention, the method includes slideably engaging the pin through any two diametrically opposed holes in the outer cylindrical body portion and through at least two diametrically opposed holes of the inner cylindrical body portion.